Performance Evaluation of a Standing Wave Thermoacoustic Refrigerator Using Normalized Sensitivity Coefficients

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Umar Nawaz Bhatti ◽  
Salem Bashmal
Keyword(s):  
Sensitivity Analysis ◽  
Standing Wave ◽  
Plate Thickness ◽  
Sensitivity Coefficient ◽  
Coefficient Of Performance ◽  
Model Parameters ◽  
Pressure Amplitude ◽  
Performance Parameters ◽  
Wide Range ◽  
Thermoacoustic Refrigerator

Abstract The sensitivity analysis using normalized sensitivity coefficient (NSC) can be used to identify important model parameters affecting the device performance by allowing one-to-one comparison. The results are highlighted in the form of order of magnitudes change in output for a unit change in input variable. In this study, the sensitivity analysis of a small capacity standing wave thermoacoustic refrigerator (SWTAR) has been performed using NSC. Specialized tool deltaec has been used to generate the results for the subsequent sensitivity analysis. Three key performance parameters, i.e., temperature difference achieved (ΔT), coefficient of performance (COP), and relative coefficient of performance (COPR) have been analyzed for perturbations in number of device variables, namely, oscillating pressure amplitude, two different stack material properties and four stack geometric parameters, i.e., stack length, stack center position, stack plate thickness, and half stack spacing. Sensitivity results are obtained for a wide range of mean operating pressures (Pm), mean operating temperature (Tm), and drive ratios (DRs). It has been found that performance parameters are most sensitive to the perturbations in oscillating pressure amplitude and least affected by the perturbations in the stack length. With respect to the oscillating pressure amplitude, maximum NSC of 24.12 has been reported for ΔT at mean pressure of 5 bar.

Modeling bronchial circulation with application to soluble gas exchange: description and sensitivity analysis

1998 ◽  
Vol 84 (6) ◽  
pp. 2070-2088 ◽  
Author(s):  
Thien D. Bui ◽  
Donald Dabdub ◽  
Steven C. George
Keyword(s):  
Sensitivity Analysis ◽  
Gas Exchange ◽  
Pulmonary Circulation ◽  
Blood Flow Rate ◽  
Latin Hypercube Sampling ◽  
Inert Gases ◽  
Phase Iii ◽  
Model Parameters ◽  
Bronchial Circulation ◽  
Wide Range

The steady-state exchange of inert gases across an in situ canine trachea has recently been shown to be limited equally by diffusion and perfusion over a wide range (0.01–350) of blood solubilities (βblood; ml ⋅ ml−1 ⋅ atm−1). Hence, we hypothesize that the exchange of ethanol (βblood = 1,756 at 37°C) in the airways depends on the blood flow rate from the bronchial circulation. To test this hypothesis, the dynamics of the bronchial circulation were incorporated into an existing model that describes the simultaneous exchange of heat, water, and a soluble gas in the airways. A detailed sensitivity analysis of key model parameters was performed by using the method of Latin hypercube sampling. The model accurately predicted a previously reported experimental exhalation profile of ethanol ( R 2= 0.991) as well as the end-exhalation airstream temperature (34.6°C). The model predicts that 27, 29, and 44% of exhaled ethanol in a single exhalation are derived from the tissues of the mucosa and submucosa, the bronchial circulation, and the tissue exterior to the submucosa (which would include the pulmonary circulation), respectively. Although the concentration of ethanol in the bronchial capillary decreased during inspiration, the three key model outputs (end-exhaled ethanol concentration, the slope of phase III, and end-exhaled temperature) were all statistically insensitive ( P > 0.05) to the parameters describing the bronchial circulation. In contrast, the model outputs were all sensitive ( P < 0.05) to the thickness of tissue separating the core body conditions from the bronchial smooth muscle. We conclude that both the bronchial circulation and the pulmonary circulation impact soluble gas exchange when the entire conducting airway tree is considered.

Analysis of uncertainty propagation through model parameters and structure

2010 ◽  
Vol 62 (6) ◽  
pp. 1230-1239 ◽  
Author(s):  
Abhijit Patil ◽  
Zhi-Qiang Deng
Keyword(s):  
Sensitivity Analysis ◽  
Standard Deviation ◽  
Dissolved Oxygen ◽  
Error Propagation ◽  
Uncertainty Propagation ◽  
Sensitivity Coefficient ◽  
Model Parameters ◽  
Hydrologic Simulation ◽  
Hspf Model ◽  
Forcing Function

Estimation of uncertainty propagation in watershed models is challenging but useful to total maximum daily load (TMDL) calculations. This paper presents an effective approach, involving the combined application of Rosenblueth method and sensitivity analysis, to the determination of uncertainty propagation through the parameters and structure of the HSPF (Hydrologic Simulation Program-FORTRAN) model. The sensitivity analysis indicates that the temperature is a major forcing function in the DO-BOD balance and controls the overall dissolved oxygen concentration. The mean and standard deviation from the descriptive statistics of dissolved oxygen data obtained using the HSPF model are compared to those estimated using Rosenblueth's method. The difference is defined as the error propagated from water temperature through dissolved oxygen. The error propagation, while considering the second order sensitivity coefficient in Rosenblueth's method, is observed to have a mean of 0.281 mg/l and a standard deviation of 0.099 mg/l. A relative low error propagation value is attributed to low skewness of dependent and independent variables. The results provide new insights into the uncertainty propagation in the HSPF model commonly used for TMDL development.

scholarly journals Sensitivity of Direct Runoff to Curve Number Using the SCS-CN Method

2019 ◽  
Vol 5 (12) ◽  
pp. 2738-2746
Author(s):  
Abdul Ghani Soomro ◽  
Muhammad Munir Babar ◽  
Anila Hameem Memon ◽  
Arjumand Zehra Zaidi ◽  
Arshad Ashraf ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Water Availability ◽  
Curve Number ◽  
Resource Planning ◽  
Model Parameters ◽  
Rainfall Runoff ◽  
Direct Runoff ◽  
Wide Range ◽  
The Impact ◽  
Scs Cn

This study explores the impact of runoff curve number (CN) on the hydrological model outputs for the Morai watershed, Sindh-Pakistan, using the Soil Conservation Service Curve Number (SCS-CN) method. The SCS-CN method is an empirical technique used to estimate rainfall-runoff volume from precipitation in small watersheds, and CN is an empirically derived parameter used to calculate direct runoff from a rainfall event. CN depends on soil type, its condition, and the land use and land cover (LULC) of an area. Precise knowledge of these factors was not available for the study area, and therefore, a range of values was selected to analyze the sensitivity of the model to the changing CN values. Sensitivity analysis involves a methodological manipulation of model parameters to understand their impacts on model outputs. A range of CN values from 40-90 was selected to determine their effects on model results at the sub-catchment level during the historic flood year of 2010. The model simulated 362 cumecs of peak discharge for CN=90; however, for CN=40, the discharge reduced substantially to 78 cumecs (a 78.46% reduction). Event-based comparison of water volumes for different groups of CN values—90-75, 80-75, 75-70, and 90-40 —showed reductions in water availability of 8.88%, 3.39%, 3.82%, and 41.81%, respectively. Although it is known that the higher the CN, the greater the discharge from direct runoff and the less initial losses, the sensitivity analysis quantifies that impact and determines the amount of associated discharges with changing CN values. The results of the case study suggest that CN is one of the most influential parameters in the simulation of direct runoff. Knowledge of accurate runoff is important in both wet (flood management) and dry periods (water availability). A wide range in the resulting water discharges highlights the importance of precise CN selection. Sensitivity analysis is an essential facet of establishing hydrological models in limited data watersheds. The range of CNs demonstrates an enormous quantitative consequence on direct runoff, the exactness of which is necessary for effective water resource planning and management. The method itself is not novel, but the way it is proposed here can justify investments in determining the accurate CN before initiating mega projects involving rainfall-runoff simulations. Even a small error in CN value may lead to serious consequences. In the current study, the sensitivity analysis challenges the strength of the results of a model in the presence of ambiguity regarding CN value.

Numerical Analysis of the Performance of an Adjustable Thermoacoustically-Driven Thermo-Acoustic Refrigerator

2019 ◽  
Author(s):  
A. C. Alcock ◽  
S. Balonji ◽  
L. K. Tartibu
Keyword(s):  
Standing Wave ◽  
Sound Wave ◽  
Coefficient Of Performance ◽  
Cooling Power ◽  
Performance Parameters ◽  
Design Environment ◽  
Resonator Length ◽  
Low Amplitude ◽  
The Relationship ◽  
Initial Results

Abstract Thermo-acoustic refrigeration could potentially become an alternative option to current traditional refrigeration systems provided that the issue related to its efficiency is addressed. One of the incentives for developing this technology is the opportunity it establishes with respect to the use of a sustainable heat source to induce cooling. Many existing works have pointed out the relationship between the geometrical configuration of the device and its performance. Mainly, the stack geometry and position have been the focus of these previous works. In this work, a standing-wave ThermoAcoustically-Driven Thermo-Acoustic Refrigerator with an adjustable resonator has been developed. Hence the device is made of two portions, joined with an adjustable duct, namely a simple standing-wave thermo-acoustic engine that converts heat into a sound wave and a simple thermo-acoustic refrigerator where heat pumping takes place. The Design Environment for Low-amplitude ThermoAcoustic Energy Conversion (DELTAEC) was used to model and analyze the influence of the adjustment of the resonator on the cooling performance. Parameters like the temperature difference across the stack, the frequency of the acoustic sound wave generated, the cooling power and the coefficient of performance have been studied. The initial results reported in this study show the possibility to change the performance of practical TADTAR by adjusting the resonator length.

scholarly journals Demonstrating of a Standing Wave - Thermoacoustic Refrigerator

2013 ◽  
Vol 06 (2) ◽  
Keyword(s):  
Temperature Variation ◽  
Standing Wave ◽  
Cfd Simulation ◽  
Plate Thickness ◽  
Full Description ◽  
Thermoacoustic Refrigerator

This manuscript begins with a full description of Thermoacoustic Refrigerator (TAR) technology followed an analysis of the elements necessary for successfully designing the various components of a TAR. The authors developed and tested a standing wave thermoacoustic refrigerator (TAR) to study the effects of stack plate thickness, load and stack temperature variation on TAR performance. They then used a CFD simulation to simulate the performance of the TAR, particularly the temperature and velocity within.

Sensitivity analysis: from model parameters to system behaviour

2008 ◽  
Vol 45 ◽  
pp. 177-194 ◽  
Author(s):  
Brian Ingalls
Keyword(s):  
Sensitivity Analysis ◽  
Operating Conditions ◽  
Model Parameters ◽  
Analytical Treatment ◽  
System Behaviour ◽  
Local Case ◽  
Wide Range ◽  
Nominal Parameter ◽  
Address System ◽  
Parameter Values

Sensitivity analysis addresses the manner in which model behaviour depends on model parametrization. Global sensitivity analysis makes use of statistical tools to address system behaviour over a wide range of operating conditions, whereas local sensitivity analysis focuses attention on a specific set of nominal parameter values. This narrow focus allows a complete analytical treatment and straightforward interpretation in the local case. Sensitivity analysis is a valuable tool for model construction and interpretation, and can be applied in medicine and biotechnology to predict the effect of interventions.

scholarly journals Steady-State Investigation of Carbon-Based Adsorbent–Adsorbate Pairs for Heat Transformation Application

2020 ◽  
Vol 12 (17) ◽  
pp. 7040 ◽  
Author(s):  
Faizan Shabir ◽  
Muhammad Sultan ◽  
Yasir Niaz ◽  
Muhammad Usman ◽  
Sobhy M. Ibrahim ◽  
...  
Keyword(s):  
Isosteric Heat ◽  
Coefficient Of Performance ◽  
Performance Parameters ◽  
Concentration Difference ◽  
Cooling Performance ◽  
Wide Range ◽  
R 134A ◽  
Heat Transformation ◽  
Adsorption Cycle ◽  
The Ideal

In this study, the ideal adsorption cycle behavior of eight activated carbon and refrigerant pairs is evaluated. The selected pairs are KOH6-PR/ethanol, WPT-AC/ethanol, Maxsorb-III/methanol, Maxsorb-III/CO2, Maxsorb-III/n-butane, Maxsorb-III/R-134a, SAC-2/R32 and Maxsorb-III/R507a. The following cooling performance parameters are evaluated for all pairs: specific cooling energy (SCE), concentration difference (ΔW) and coefficient of performance (COP) of ideal adsorption cooling and refrigeration cycles. The evaporator temperatures for the applications of adsorption cooling and refrigeration are selected as 7 and −5 °C, respectively. It is found that the Maxsorb-III/methanol pair has shown the highest specific cooling energy and coefficient of performance in a wide range of desorption temperatures; i.e., for the adsorption cooling cycle it has SCE and COP of 639.83 kJ/kg and 0.803, respectively, with desorption temperatures of 80 °C. The KOH6-PR/ethanol and the WPT-AC/ethanol pairs also give good performances comparable to that of the Maxsorb-III/methanol pair. However, the SAC-2/R32 pair possesses a higher concentration difference than the Maxsorb-III/methanol, KOH6-PR/ethanol and WPT-AC/ethanol pairs but shows a lower performance. This is due to the lower isosteric heat of adsorption of SAC-2/R32 compared to these pairs. It is found that Maxsorb-III/methanol, KOH6-PR/ethanol and WPT-AC/ethanol are the most promising pairs for application in designing adsorption cooling and refrigeration systems.

scholarly journals Advanced sensitivity analysis of the impact of the temporal distribution and intensity of rainfall on hydrograph parameters in urban catchments

2021 ◽  
Vol 25 (10) ◽  
pp. 5493-5516
Author(s):  
Francesco Fatone ◽  
Bartosz Szeląg ◽  
Adam Kiczko ◽  
Dariusz Majerek ◽  
Monika Majewska ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Logistic Regression ◽  
Temporal Distribution ◽  
Sensitivity Coefficient ◽  
Model Parameters ◽  
Hydrodynamic Models ◽  
Sensitivity Coefficients ◽  
Urban Catchments ◽  
Outflow Hydrograph ◽  
The Impact

Abstract. Knowledge of the variability of the hydrograph of outflow from urban catchments is highly important for measurements and evaluation of the operation of sewer networks. Currently, hydrodynamic models are most frequently used for hydrograph modeling. Since a large number of their parameters have to be identified, there may be problems at the calibration stage. Hence, sensitivity analysis is used to limit the number of parameters. However, the current sensitivity analytical methods ignore the effect of the temporal distribution and intensity of precipitation in a rainfall event on the catchment outflow hydrograph. This article presents a methodology of constructing a simulator of catchment outflow hydrograph parameters (volume and maximum flow). For this purpose, uncertainty analytical results obtained with the use of the GLUE (generalized likelihood uncertainty estimation) method were used. A novel analysis of the sensitivity of the hydrodynamic catchment models was also developed, which can be used in the analysis of the operation of stormwater networks and underground infrastructure facilities. Using the logistic regression method, an innovative sensitivity coefficient was proposed to study the impact of the variability of the parameters of the hydrodynamic model depending on the distribution of rainfall, the origin of rainfall (on the Chomicz scale), and the uncertainty of the estimated simulator coefficients on the parameters of the outflow hydrograph. The developed model enables the analysis of the impact of the identified SWMM (Storm Water Management Model) parameters on the runoff hydrograph, taking into account local rainfall conditions, which have not been analyzed thus far. Compared with the currently developed methods, the analyses included the impact of the uncertainty of the identified coefficients in the logistic regression model on the results of the sensitivity coefficient calculation. This aspect has not been taken into account in the sensitivity analytical methods thus far, although this approach evaluates the reliability of the simulation results. The results indicated a considerable influence of rainfall distribution and intensity on the sensitivity factors. The greater the intensity and rainfall were, the lower the impact of the identified hydrodynamic model parameters on the hydrograph parameters. Additionally, the calculations confirmed the significant impact of the uncertainty of the estimated coefficient in the simulator on the sensitivity coefficients. In the context of the sensitivity analysis, the obtained results have a significant effect on the interpretation of the relationships obtained. The approach presented in this study can be widely applied at the model calibration stage and for appropriate selection of hydrographs for identification and validation of model parameters. The results of the calculations obtained in this study indicate the suitability of including the origin of rainfall in the sensitivity analysis and calibration of hydrodynamic models, which results from the different sensitivities of models for normal, heavy, and torrential rain types. In this context, it is necessary to first divide the rainfall data by origin, for which analyses will be performed, including sensitivity analysis and calibration. Considering the obtained results of the calculations, at the stage of identifying the parameters of hydrodynamic models and their validation, precipitation conditions should be included because, for the precipitation caused by heavy rainfall, the values of the sensitivity coefficients were much lower than for torrential ones. Taking into account the values of the sensitivity coefficients obtained, the calibration of the models should not only cover episodes with high rainfall intensity, since this may lead to calculation errors at the stage of applying the model in practice (assessment of the stormwater system operating conditions, design of reservoirs and flow control devices, green infrastructure, etc.).

Experimental Investigation on the Performance of the Air-based Standing Wave Thermoacoustic Refrigerator using Heat Pipe as Heat Exchangers

2020 ◽  
Vol 28 (01) ◽  
pp. 2050007
Author(s):  
Praitoon Chaiwongsa ◽  
Somchai Wongwises
Keyword(s):  
Heat Exchanger ◽  
Standing Wave ◽  
Thermoelectric Module ◽  
Heat Pipes ◽  
Acoustic Power ◽  
Coefficient Of Performance ◽  
Cooling Load ◽  
Heat Absorber ◽  
Cooling Loads ◽  
Thermoacoustic Refrigerator

The coefficient of performance (COP) and relative coefficient of performance (COPR) of the standing wave thermoacoustic refrigerator (SWTAR) were investigated. The components of the SWTAR are a resonator tube, a stainless-steel bowl-shaped resonator cone, a commercial loudspeaker, a spiral stack, a cold side heat exchanger (CSHX) with miniature heat pipes (MHPs) and a hot side heat exchanger (HSHX). An operating frequency of 163[Formula: see text]Hz was used in this study, with an acoustic power (AP) supply of 10, 20 and 30[Formula: see text]W. Cooling loads were heat provided from a thermoelectric module (TEM) by joining the hot side of the TEM to the copper heat absorber and transferring heat to the CSHX through MHPs. The COP of the SWTAR increased with increasing cooling load. The slopes of the COP curves decreased with increasing AP. The COPR of the SWTAR increased with increasing cooling load until it was approximately 30% of AP.

Effects of the Optimized Resonator Dimensions on the Performance of the Standing-Wave Thermoacoustic Refrigerator

2016 ◽  
Vol 819 ◽  
pp. 63-68
Author(s):  
Mawahib Hassan El-Fawal ◽  
Normah Mohd-Ghazali ◽  
Mohd Shafiek Yaccob
Keyword(s):  
Standing Wave ◽  
Cooling System ◽  
Small Diameter ◽  
Acoustic Power ◽  
Diameter Ratio ◽  
Coefficient Of Performance ◽  
Resonator Length ◽  
Environmentally Safe ◽  
And Performance ◽  
Thermoacoustic Refrigerator

Thermoacoustic refrigerator is an alternative cooling system, which is environmentally safe due to the absence of any refrigerants. The resonator tube of the system is of great importance; its design and dimensions influence the design and performance of the entire refrigerator. This work describes the design of the stack and the resonator along with the influence of its dimensions on the performance of the standing-wave thermoacoustic refrigerator. The resonator consists of two tubes, one larger than the other, characterized by the diameter ratio of the smaller over the larger diameter. A Lagrange multiplier method is used as a technique to optimize the coefficient of performance (COP) of the system. Results show that the resonator small diameter tube dissipates a minimum acoustic power at a diameter ratio of 0.46, which is 17 percent less than the published values. Moreover, the results show that the resonator length increases gradually with the increase of the mean design temperature which leads to the increase of the total acoustic power dissipated by the resonator, reducing the COP of the standing-wave thermoacoustic refrigerator.

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